The National Capital Planning Commission gave final approval Monday to a new security configuration for a memorial to Martin Luther King Jr., clearing the way for construction of the long-awaited monument.

There were tears in the audience when the capital's federal planning agency voiced its unanimous approval at a specially arranged meeting. "Very big day," said Trudy D. Byrd, memorial project public relations manager, as she wiped away tears. ""It's been a long time coming."

Ed Jackson Jr., the memorial project's chief architect, said: "This is 12 years, personally, of my involvement. . . . The light has turned green. All we're looking at now is that building permit from the Park Service."

The memorial is planned for a four-acre crescent-shaped site amid the cherry blossoms on the northwest shore of the Tidal Basin. The centerpiece is to be a 2 1/2 -story granite sculpture of the slain civil rights leader. Called the Stone of Hope, it depicts King standing with his arms folded as if emerging from the stone.

At 28 feet, it will be eight feet taller than the statue of Abraham Lincoln in the memorial to the 16th president and will rest on pilings driven as far as 50 feet down to bedrock.

The project has weathered several storms. It was criticized when organizers picked a sculptor in China to execute the design. Then the original sculpture of King was assailed as too "confrontational" by the Federal Commission of Fine Arts and had to be reworked slightly. The project later stalled amid debate over how much security is needed at the site.

The National Park Service, concerned about car bombs, wanted a series of stout bollards, or security pillars, at the main entrance and elsewhere. Critics said that ran counter to King's sense of openness.

The compromise calls for a low-walled island containing two large elm trees as the main vehicle barrier to the site's entrance. There will be security bollards, but they will be less apparent, and the trees will frame and insulate the site from the street, officials said.

"I'm appreciative, and I look forward to the next step as we go forward," said Harry E. Johnson Sr., president and chief executive of the memorial's foundation.

Monday's action came at a special commission meeting requested by the Interior Department. It "was of particularly high priority to Secretary (Ken) Salazar because of Dr. King's legacy and the importance of the proposed memorial in his honor," a department spokeswoman said in an e-mail. The Interior Department will oversee the site.

The sculpture of King and other parts of the memorial are being crafted in 144 blocks by Chinese master sculptor Lei Yixin. The pieces must be transported to the United States by sea, officials have said.

Peter May, an associate regional director with the Park Service, said the construction permit likely will be issued in a matter of days, after a final review of the building plans. The project also must contribute to the long-term preservation of the $120 million memorial and its site, he said. The project has raised $107 million so far.

The memorial's anticipated completion date is late summer 2011, Jackson said Monday.